import java.util.Scanner;

public class java20231124 {
    public static void main(String[] args) {
//        int[] arr={2,2,1,1,1,2,2};
//        int[] arr1={3,2,3};
        Scanner sc = new Scanner(System.in);
        String str = sc.next().toString();
        String[] arr = str.split(",");
        int i = 0;
        int j = 0;
        for(i = 0;i < arr.length ; i ++){
            int count = 0;
            for(j = 0; j < arr.length ;j++){
                if(arr[j] == arr[i]){
                    count++;
                }
            }
            if(count > arr.length/2){
                System.out.println(arr[i]);
                break;
            }
        }
    }
}
